Atomic layer deposition of metal oxide materials for memory applications

Abstract

Embodiments of the invention generally relate to nonvolatile memory devices, such as a ReRAM cells, and methods for manufacturing such memory devices, which includes optimized, atomic layer deposition (ALD) processes for forming metal oxide film stacks. The metal oxide film stacks contain a metal oxide coupling layer disposed on a metal oxide host layer, each layer having different grain structures/sizes. The interface disposed between the metal oxide layers facilitates oxygen vacancy movement. In many examples, the interface is a misaligned grain interface containing numerous grain boundaries extending parallel to the electrode interfaces, in contrast to the grains in the bulk film extending perpendicular to the electrode interfaces. As a result, oxygen vacancies are trapped and released during switching without significant loss of vacancies. Therefore, the metal oxide film stacks have improved switching performance and reliability during memory cell applications compared to traditional hafnium oxide based stacks of previous memory cells.

The invention claimed is: 
     
       1. A device comprising:
 a first electrode disposed on a substrate; 
 a host layer disposed on the first electrode,
 the host layer comprising an exposed surface; and 
 
 a coupling layer over the host layer,
 wherein the coupling layer and the host layer form a misaligned grain interface, 
 the misaligned grain interface facilitating oxygen vacancy exchange between the coupling layer and the host layer. 
 
 
     
     
       2. The device of  claim 1 , wherein the host layer comprises a crystalline metal-rich oxide. 
     
     
       3. The device of  claim 2 , wherein the crystalline metal-rich oxide is represented by a generic chemical formula of MO x , wherein M comprises one of hafnium, zirconium, or titanium, and wherein X is within a range from about 1.65 to about 1.95. 
     
     
       4. The device of  claim 3 , wherein X is within a range from about 1.70 to about 1.90. 
     
     
       5. The device of  claim 1 , wherein the coupling layer comprises an amorphous metal-rich oxide. 
     
     
       6. The device of  claim 5 , wherein the amorphous metal-rich oxide is represented by a generic chemical formula of MM′ Y O Z , wherein M comprises one of hafnium, zirconium, or titanium, M′ comprises one of aluminum, yttrium, or lanthanum, wherein Y is within a range from about 0.05 to about 0.50, and wherein Z is within a range from about 1.50 to about 2.50. 
     
     
       7. The device of  claim 6 , wherein Y is within a range from about 0.05 to about 0.15, and wherein Z is within a range from about 1.50 to about 2.10. 
     
     
       8. The device of  claim 6 , wherein Y is within a range from about 0.40 to about 0.50, and wherein Z is within a range from about 2.10 to about 2.50. 
     
     
       9. The device of  claim 1 , wherein the host layer comprises a crystalline metal-rich oxide of a first metal, wherein the coupling layer comprises an amorphous metal-rich oxide of a second metal, and wherein the first metal and the second metal are same. 
     
     
       10. The device of  claim 1 , further comprising a silicon oxide layer between the first electrode and the host layer. 
     
     
       11. The device of  claim 10 , wherein the silicon oxide layer has a thickness of between about 2 Angstroms and 40 Angstroms. 
     
     
       12. The device of  claim 1 , wherein the host layer has a thickness of between about 5 Angstroms and 100 Angstroms. 
     
     
       13. The device of  claim 1 , wherein the coupling layer has a thickness of between about 3 Angstroms and 80 Angstroms. 
     
     
       14. The device of  claim 1 , wherein an average grain size of a material forming the host layer is greater than an average grain size of a material forming the coupling layer thereby causing the misaligned grain interface. 
     
     
       15. The device of  claim 14 , wherein a ratio of the average grain size of the material forming the host layer to the average grain size of the material forming the coupling layer is between about 1.05 and 2.0. 
     
     
       16. The device of  claim 14 , wherein a ratio of the average grain size of the material forming the host layer to the average grain size of the material forming the coupling layer is between about 1.10 and 1.50. 
     
     
       17. The device of  claim 14 , wherein the average grain size of the material forming the host layer is between about 30 nanometers and 40 nanometers. 
     
     
       18. The device of  claim 1 , wherein the host layer comprises hafnium oxide, and wherein the coupling layer comprises hafnium aluminate. 
     
     
       19. The device of  claim 18 , wherein a concentration of aluminum in the coupling layer is between about 20% atomic and 60% atomic relative to a concentration of hafnium. 
     
     
       20. The device of  claim 18 , wherein a concentration of aluminum in the coupling layer is between about 2% atomic and 20% atomic relative to a concentration of hafnium.